Improper privilege management in Mozilla Firefox and Firefox for Android - CVE-2026-109739
Published: October 16, 2026
Vulnerability identifier: #VU156058
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-109739
CWE-ID: CWE-269
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to escalate privileges.
The vulnerability exists due to improper privilege management in the WebExtensions component when handling extension-related operations. A remote attacker can exploit the component's privilege-handling flaw to gain privileges beyond those intended.
Affected software
Mozilla Firefox
Firefox for Android
Firefox for Android
How to mitigate CVE-2026-109739
Install security update from vendor's website.
Mozilla Firefox - update to 158.0
Firefox for Android - update to 158.0
Firefox for Android - update to 158.0